1. Field of the Invention
This invention relates to reusable pressurized containers for dispensing fluids without release of the liquefiable propellant used to dispense the fluid to the surrounding atmosphere, to a method of making such containers and to fluid reservoir systems employing a pressurized liquefiable propellant.
2. Description of the Prior Art
Dispensing containers are widely used to dispense a myriad of products. Conventional pressurized dispensers generally use a propellant in solution with the product to be dispensed which is usually discharged along with the product into the atmosphere and which evaporates instantly upon discharge, helping break the product into a fine mist. The propellants commonly used include halogenated hydrocarbons, such as difluorodichloromethane and dichlorotetrafluoroethane, and aliphatic hydrocarbons, such as propane, isobutane, n-butane and mixtures thereof.
Recent concern has been expressed by scientists about the effects of discharge of fluorocarbon propellants into the atmosphere where they accumulate in the upper atmosphere and cause possible depletion of the ozone layer enveloping the earth. Such concern has resulted in regulations to curtail the use of such propellants. Hydrocarbon propellants such as propane, isobutane, butane and others, while not creating an environmental problem, pose a safety hazard during storage and transportation because of their combustability, particularly when the container is discarded when not completely empty.
It is expected that free discharge of fluorocarbons into the atmosphere will be banned world-wide in the near future. Except for personal products and some food products, most of the users of fluorocarbon propellants are expected to switch to hydrocarbon propellants. Should this switchover take place, annual consumption of propane and isobutane as propellants would increase from 100,000,000 pounds in 1971 to more than 1,000,000,000 pounds in the near future, equivalent to about 24 billion cu. ft. of natural gas at atmospheric pressure in the United States alone. This is a significant amount of fuel on an annual basis which could be better used to supply factories and provide employment. At the same time, probable safety hazards from the use of more hydrocarbon-filled aerosol cans will increase many times as fluorocarbon use will likely be phased out in blending with hydrocarbon propellants to reduce their flammability as a flame suppressant. With the containers described herein, the total consumption of hydrocarbons could be a very small fraction of one percent of that used at present.
From the standpoint of (1) environmental protection of the ozone layer, (2) conservation of fuel energy, and (3) safety for the consumer and the public, the containers described herein are a solution to a serious problem.
Dispensers such as those disclosed in U.S. Pat. Nos. 3,460,714; 3,578,210; 3,815,793; and 3,858,764, release the propellant into the atmosphere with the product to be dispensed.
U.S. Pat. No. 3,417,901 describes a reusable pressurized dispenser wherein a propellant which can be liquefied in a home refrigerator and which boils below operating temperture, is sealed in a flexible container in contact with the material to be dispensed. The propellant, when warmed to ambient temperature, forces the material to be dispensed out of the container. The container is refilled by cooling the container to liquefy the propellant and then opening the container to add more material to be dispensed.
U.S. Pat. No. 2,930,513 describes a pressurized liquid dispenser employing a compressed air propellant.
U.S. Pat. No. 3,233,791 utilizes a propellant operated gel piston which is prone to leakage with release of the propellant to the atmosphere as the product is dispensed.
U.S. Pat. No. 3,659,395 utilizes a closed cell foam material within a container. Propellant is injected into the container under pressure which diffuses through the walls of the foam into the foam cells. The product to be dispensed is then injected under pressure into the container. The propellant is not sealed but is released as the product is dispensed.
There remains a need for a pressurized dispenser which can be reused repeatedly without release of the propellant to the atmosphere which can be manufactured economically.
Pressurized fluid reservoir systems currently used in the industry are, in some instances, of inadequate holding capacity for the same size unit and are not constant pressure systems.